Generally, the sheet of plastic material is stretched between two substantially straight opposite edges, particularly between two walls, to constitute a false ceiling. A sheet of plastic material ordinarily has an integral margin which is both supple and rigid, whose cross section is in the form of a hook that grasps the shoulder provided on the fixed supports secured directly to the wall or against the ceiling.
It is known to use profiles generally of extruded material, as supports comprising a shoulder on which is fixed the margin of the sheet of plastic material, the cross sections of these borders having several variations in their construction, so as to ensure their hooking function. The coaction of the hook constituted by the border, and the shoulder, formed on the profile, permits supporting and maintaining in tension the false ceiling or the false wall.
The principal difficulty involved in the conception and production of the profile and of the integral border of the sheet of plastic material, is the positioning, the hooking and the tensioning of the false ceiling or false wall.
Generally, the material constituting the sheet of plastic material stretches when the temperature rises. For this reason, on the one hand, the size of the false ceiling or false wall is, before installation, slightly less than the finished dimension, and, on the other hand, it is indispensable to heat strongly the false ceiling or false wall in the course of installation, as well as the member in which the one end or the other is to be installed.
The installation conditions are not very comfortable, on the one hand, because of the high temperature of the site, and on the other hand, because the operator, particularly to install a false ceiling, is most often located below this false ceiling to hook it onto the profiles fixed against the walls.
To facilitate the emplacement of the border, certain profiles have a rounded surface such that the border slides before becoming wedged in (FR-A-2 078 579), or cut panels are provided to fulfill an equivalent role, as described in FR-A-2 310 450 and FR-A-2 475 093.
Despite the flexibility of the border, it is generally difficult to engage the lip forming the hook over all the length of the shoulder provided on the profile, such that it is necessary to proceed progressively. To maintain in place the border on a certain section of the shoulder provided on the profile, before proceeding to another section, there are generally provided mortises on this shoulder, so as to limit the length of hooking, and to proceed by stretches of about 20 cm according to FR-A-310 450 or about 12 cm according to FR-A-2 475 093.
To this end, as soon as the first section is engaged, it is indispensable to mark the mortises which are not visible when the operator is situated below the profile. To avoid the need to make a preliminary marking or to proceed by touch, a device comprising a profile with a shoulder without mortises coacts with a border forming a hook on which are provided mortises similar to those provided on the shoulder, as taught by FR-A-2 688 849.
However, these mortises, in addition to the fact that they weaken the profiles or the border, require remachining after extrusion, according to a process generally used. Such an operation is burdensome and substantially increases the cost of the profile or of the border.
Moreover, the profiles are more or less spaced from the surface of the wall on which they are fixed, such that, either their size, or their spacing, is unattractive. To this end, one of the proposed profiles comprises, in its lower portion, a shoulder adapted to cast a shadow and which can serve as an ogee (FR-A-2 078 579).
For aesthetic reasons, it is also possible to position, in the lower part of the profile fixed against the wall, a compensating profile hiding the hook system of the border fixed by jamming between the profile and its shoulder (FR-A-2 624 167).
Generally, to cover all the surface of a ceiling or a wall, the false ceilings and false walls are made in several panels welded together by high frequency current.
When the surface is not too extensive, the tension of the sheet of plastic material is sufficient to avoid the material's own weight, although small per square meter, creating an important sag in the center of the piece.
For large surfaces and to avoid this unsightly sag, it is necessary to fix to the ceiling, at the middle thereof, profiles forming intermediate supports and serving to hook the edges of the two adjacent integral panels with borders forming hooks.
However, the profiles used are generally variations of the profiles serving for the securement against the ceiling and permitting hooking of two edges (FR-A-2 078 579 and FR-A-2 310 450).
The types of profiles serving as intermediate supports, fixed generally to the middle of the construction, can be considered unsightly. To this end, it is proposed to use the junction of the panels to ensure the suspension of the sheet of plastic material from the ceiling. This solution permits moreover mounting a false ceiling according to the shape of the ceiling itself, when this latter is not perfectly horizontal or when its profile is a broken line, particularly for mansard peaks (EP-A-0 13 7 086).
Other solutions require aesthetically securing the false ceiling to the center of the location and provide profiles adapted to be fixed against the wall, the ceiling, or serving at the same time to maintain the border of a false ceiling and of a false wall, thus hiding the profile. To this end, the border is fixed by wedging with the help of a simple spatula, masks or decorations being fixed by clips on the profiles (EP-A-0 338 925).
All the profiles proposed are generally cumbersome, either because they require machining to effect a mortise necessary for emplacing the false ceiling or false wall, or because they are provided each for a specific use, such that it is necessary to store several types of profiles for a predetermined use. To provide profiles at reasonable price, most builders use profiles of plastic material. These profiles, weakened by the mortises, are less rigid than the profiles extruded from light metal. Moreover, their painting is difficult because it does not cling to the plastic and requires repainting because of flaking accidentally happening during adjustments necessary for installation.
No matter what the system of hooking of the border that is used, using a hook and mortises or a system of jamming on the shoulder, the operation of installation remains delicate because of the fragility of the sheet of plastic material and also because of the conditions of installation, most often high overhead and at elevated temperature.
Moreover, from a decorative standpoint it may be interesting to combine these types of false ceilings or false walls with ceiling or wall portions constituted by panels or sunken panels of different materials, such as linings or mirrors, or different uses, such as lights. The profiles dedicated to the false ceilings and false walls generally are not adaptable for such use.
Without changing the conditions of installation, the present invention proposes to facilitate them and to overcome the drawbacks recited above.